3.7 Homeostatic Regulation of Cardiovascular Function Flashcards
When is the cardiac output lowest? What is it?
When someone has been lying down. Pressure is around 4-5L/min
What is the maximum cardiac output? When does it happen?
During exercise. About 20-25L/min
What is the equation for cardiac output?
Cardiac Output = Stroke Volume x Heart Rate
What is the Frank-Starling Mechanism?
Venous return controls cardiac output. As atrial pressure increases, ventricular output increases. Like stretching the arm (or ventricle) before throwing a ball.
How does hypovolemia relate to the Frank-Starling mechanism?
- Fluid return decreases, ventricular output decreases.
Why does increase in stretch result in increased contractility?
As the muscle is stretched, calcium sensitivity increases, resulting in increased contractility. Length is proportional to tension.
How does the difference between active and passive stretch influence force output.
Bigger difference, bigger force output
What is a chronotropic effect?
Increasing ventricular rate
What is ionotropic effect?
Change in the amount of force with which cardiac muscle fibres contract
What does parasympathetic stimulation do to the heart?
Supresses heart rate and modestly reduces contractility
What effects does sympathetic innervation have on the heart?
Ionotropic and chonotropic
What is the intrinsic heart rate (with no effect of parasympathetic or sympathetic)
100-110bpm
How can the endocrine system influence cardiac function?
- Noradrenaline can be released into target organs by nerve endings.
- Adrenaline and noradrenaline can be transported to the target organ through the bloodstream
Is there more adrenaline or noradrenaline released during the sympathetic stimulatoin of the adrenal medulla? Is this a short or long-lasting effect?
Andrenaline (about 80%). This is a longer lasting effect?
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